DNA Replication Mechanisms and Enzymes

Vocabulary flashcards covering the models, structures, and enzymes involved in bacterial and eukaryotic DNA replication.

Semiconservative model

The model of DNA replication predicting that each produced daughter DNA molecule consists of one old parental strand and one newly synthesized strand.

Conservative model

A disproven model of DNA replication predicting that one daughter DNA molecule is composed entirely of two parental strands, while the other daughter molecule is composed entirely of newly synthesized DNA.

Dispersive model

A disproven model of DNA replication predicting that daughter DNA molecules contain a mixture of both old parental DNA and newly synthesized DNA interspersed within both strands.

Matthew Meselson and Franklin Saul

Researchers who used bacteria grown in nitrogen-15 heavy isotope and transferred to lighter isotope media with centrifugation to disprove the conservative and dispersive models of DNA replication.

Origin of replication

Specific sites in the DNA where double-stranded DNA is separated to form single strands and initiate the process of DNA replication.

Replication bubble

An unwound region where double-stranded DNA has been converted to single-stranded DNA so that replication can proceed bidirectionally.

Replication fork

A Y-shaped structure located at each end of a replication bubble where double-stranded DNA is actively being converted to single-stranded DNA.

DNA helicase

An enzyme that unwinds double-stranded DNA into single-stranded DNA at the replication fork by breaking the hydrogen bonds connecting the complementary strands.

Single-stranded binding proteins

Proteins that bind to single-stranded DNA within the replication bubble to stabilize it so replication can occur.

Topoisomerases (Gyrases)

Enzymes that relieve supercoiling by breaking phosphodiester bonds in the DNA backbone, swiveling or rotating the backbone, and reforming the phosphodiester bonds.

RNA primase

An enzyme that synthesizes a short single-stranded RNA primer that is $5$ to $10$ nucleotides long and base pairs it to the template DNA strand.

RNA primer

A short sequence of RNA ($5$ to $10$ nucleotides long) added to single-stranded DNA that is required for DNA polymerase to bind and initiate synthesis.

DNA polymerase

An enzyme that catalyzes the synthesis of single-stranded DNA by adding nucleotides sequentially to the $3'$ end of a primer or growing DNA strand using a template strand.

Nucleoside triphosphate

A monomer molecule consisting of a nucleotide attached to three phosphate functional groups, used by DNA polymerase to build the new DNA strand.

dATP (Deoxyribose ATP)

A nucleoside triphosphate containing a deoxyribose sugar that supplies adenine nucleotides to a growing DNA strand.

Pyrophosphate

A molecule consisting of two connected phosphate groups that is released along with a water molecule during the dehydration reaction that adds a nucleotide to a growing DNA strand.

Leading strand

The new DNA strand that is synthesized continuously in one piece moving in the $5'$ to $3'$ direction toward the replication fork and away from the origin of replication.

Lagging strand

The new DNA strand synthesized discontinuously in segments moving away from the replication fork and toward the origin of replication.

Okazaki fragments

Short segments of DNA synthesized discontinuously along the lagging strand.

DNA polymerase III

A DNA polymerase that binds to the RNA primer made by primase and synthesizes single-stranded DNA in the $5'$ to $3'$ direction.

DNA polymerase I

An enzyme that removes RNA primers and replaces the RNA nucleotides with DNA nucleotides.

DNA ligase

An enzyme that joins Okazaki fragments together on the lagging strand by forming phosphodiester bonds.